When I installed OpenBSD 3.4 on really old hardware I had some trouble booting the system. When 'boot' was
checking for the attached hardrives, it took for almost 10 minutes to detect that there were no master or slave
on the secundary harddrive-controller. This had nothing to do with hardware-problems because the machine had previously run
Linux for 3 years without any trouble.

In the file diskprobe.c there is a loop that counts from 0x80 to 0x88. When I modified this to 0x82
(and so indicating that it should only check for two drives) my system booted properly, without long timeouts. Now, it takes a little more than just
modifying this file. These are the steps that I do. Off course, when you're going to add drives, you need to adjust the values to your need.

If you already have the sources then you can skip the first two steps (in fact, I'm not really sure they are needed).

Copy all the files to this location (this will copy /usr/local to the new location)

cd /usr/local; find -d . -print | cpio -pvdum /mnt/tmp

Update the file /etc/fstab with the new location.

/dev/wd0j /usr/local ffs rw 1 1

Now reboot into single user mode (issue boot -s on the boot-prompt)
Move the existing directory to an new location and create a new one. Watch it, it is possible that you have to mount /usr in the case that you are moving /usr/local.